Ground-based remote sensing measurements of CO2 and CH4 using the moon as light source during the polar night

在过去的几年里，利用近红外光谱区域的地面太阳吸收遥感光谱技术，已经发展了测量大气CO2和CH4总柱的技术，具有足够的精度。这些观测在国际上由全柱碳观测网络（TCCON）组织。这些观测已经开始用于卫星验证，因为它们以与卫星相似的方式对大气进行采样。然而，人们发现测量本身对于研究微量气体的来源和汇极有价值，因为与地面原位数据相比，地面总柱数据的解释较少依赖于对大气中垂直混合的假设。我们在斯匹次卑尔根岛（北纬79°）的北极高纬度地区进行这样的观测。然而，在10月至3月中旬的极夜期间，由于太阳在地平线以下，无法进行观测。由于二氧化碳的季节循环在北纬高纬度地区最大，因此缺乏冬季的总柱数据限制了我们对碳收支的理解。在这个项目中，我们计划修改测量和分析技术，在极夜使用月球作为光源测量近红外CO2和CH4的总柱数。这将使我们能够在满月前后±3天进行观测，从而获得整个极夜大约三个满月周期的数据。这样就可以测量北极高纬度地区CO2和CH4总柱测量的完整季节周期，这是迄今为止尚不清楚的。最后，将整个数据集与该站点现有的原位地表数据进行比较，并将原位和总柱数据集与适当的模型进行比较。

Throughout the last years measurement techniques have been developed to measure total columns of atmospheric CO2 and CH4 with sufficient precision using the ground-based solar absorption remote sensing spectrometry in the near-infrared spectral region. These observations are internationally organized in the Total Column Carbon Observing Network (TCCON). These observations have been initiated for the satellite validation, because they sample the atmosphere in a similar way as satellites. However, the measurements itself have been found extremely valuable to investigate the sources and sinks of the trace gases, because the interpretation of the ground-based total column data depend to a less extent on assumptions on the vertical mixing in the atmosphere compared to surface in-situ data. We perform such observations at our site in the high Arctic on Spitsbergen (79°N). However, during the polar night from October until mid March no observations can be performed, because the sun is below the horizon. Since the seasonal cycle of CO2 is largest in the high northern latitudes the lack of total column data for the winter period limits our understanding of the carbon budget. Within this project we plan to modify the measurement and analysis technique to measure the total columns of CO2 and CH4 in the near-infrared using the moon as light source during the polar night. This will allow us to perform observations on ±3 days around full moon, and thus, obtain data throughout the polar night for about three full moon periods. This allows measuring the complete seasonal cycle of total column measurements of CO2 and CH4 in the high Arctic, which is not known so far. Finally, the whole set of data will be compared to the existing in-situ surface data at that site and both data sets, in-situ and total column, will be compared with appropriate models.